There is known an osmotic pump utilizing an osmosis phenomenon in which liquid moves through a semipermeable membrane. As an example of a technology utilizing osmosis, Japanese Patent Application Laid-Open No. S58-054962 discloses one in which osmosis is utilized in a liquid extraction pump.
Japanese Patent Application Laid-Open No. H06-094669 also discloses a technology in which solvent is moved by utilizing osmosis to generate a pump function. The publication discloses a technology in which there is provided an osmotic container in which an aqueous solution chamber previously filled with aqueous solution and a water-filled chamber are separated from each other by a semipermeable membrane, osmotic pressure being generated by filling the water filled chamber with water.
With recent development of a three-dimensional fine processing technology, attention is being focused on a system in which there are integrated on a substrate of glass, silicon, or the like a minute flow path, liquid devices such as a pump and a valve, and a sensor, chemical analysis being conducted on the substrate. Such a system as described above is known by the name of micro scale total analysis systems (μTAS). There have been proposed provisions, within a substrate, of minute structures such as a micro channel forming a flow path of a predetermined configuration and a port, and execution of various operations such as chemical reaction, synthesis, refinement, extraction, production, and analysis of a substance in the minute structure. A part of the proposal has been put into practice. The structure which has minute structures such as a micro channel and a port within a substrate is generally referred to as a “microchip.”
A microchip is applicable to a wide variety of uses such as gene analysis, clinical diagnosis, medicine screening, and environmental monitoring. A microchip has various advantages, such as (1) a markedly small use amount of the sample and reagent, (2) short analysis time, (3) high sensitivity, (4) portability allowing analysis on the spot, and (5) disposability.
In such a microchip as described above, it is necessary to accurately weigh the liquid component such as reaction liquid, reagent solution, or sample solution, and to deliver the liquid component accurately to a desired position in the channel in the chip.
In view of this, there is a strong demand for development of a microchip as disclosed in Japanese Patent Application Laid-Open No. 2004-053371, and development of a unit capable of accurately weighing the liquid component within the chip and accurately delivering the weighed liquid component to an arbitrary position.
If it is possible to utilize an osmotic pump as described above as the liquid supply drive unit of a microchip, a microchip suitable for solving the above-mentioned problem may be developed. However, no attempt in this line has been made yet.